Program for Supernova Data Fitting

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COSMOMC is a commonly used program for fitting Supernova data to constrain cosmological model parameters, although it is not very user-friendly. Users can input {z,M} data into a spreadsheet like Excel to derive {z,Dm} pairs using the formula Dm = (10^(M/5))/(1+z). To compare results with the LCDM model, integrating software is necessary to analyze the relationship between Dm and the time integral of the scale factor. The integration limits range from the time when the scale factor equals 1/(1+z) to the present time. Overall, COSMOMC is a key tool in this area despite its complexity.
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Are there any programs which could be used to fit the Supernova data to constrain the cosmological models's parameter? thx
 
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micomaco86572 said:
Are there any programs which could be used to fit the Supernova data to constrain the cosmological models's parameter? thx
Well, sort of. Many physicists use COSMOMC for this kind of work. It isn't, however, very user-friendly.
 
You can drop the {z,M} points into a spread sheet like Excel and take Dm = (10^(M/5))/(1+z) to get {z,Dm} pairs, which are well-behaved (Dm approx az - bz²). You'll need some integrating software to compare the LCDM model which predicts that "a" is proportional to sinh(qt) where q is a constant that depends on the parameters. Then Dm is proportional to the time integral of (1/a)dt. The limits are from the time tz where a(tz) = 1/(1+z) to the present time t0 (which is fixed).
 
Chalnoth said:
Well, sort of. Many physicists use COSMOMC for this kind of work. It isn't, however, very user-friendly.
thank u Chalnoth. I have heard about this program, but I forgot the name.
 
https://en.wikipedia.org/wiki/Recombination_(cosmology) Was a matter density right after the decoupling low enough to consider the vacuum as the actual vacuum, and not the medium through which the light propagates with the speed lower than ##({\epsilon_0\mu_0})^{-1/2}##? I'm asking this in context of the calculation of the observable universe radius, where the time integral of the inverse of the scale factor is multiplied by the constant speed of light ##c##.
Why was the Hubble constant assumed to be decreasing and slowing down (decelerating) the expansion rate of the Universe, while at the same time Dark Energy is presumably accelerating the expansion? And to thicken the plot. recent news from NASA indicates that the Hubble constant is now increasing. Can you clarify this enigma? Also., if the Hubble constant eventually decreases, why is there a lower limit to its value?
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